Laser depilating method and laser depilating apparatus

ABSTRACT

A laser depilating method for depilating treatment by irradiating a skin surface with a laser beam emitted from a semiconductor laser. A treatment region of the skin surface is treated with a semiconductor laser beam for an irradiation time of 100 msec or more per irradiation while controlling the laser beam so that the energy density when irradiating the skin surface may be in a range of 0.01–1 J/mm 2 . Irradiation of the skin surface with a semiconductor laser beam under such a condition provides a more secure and efficient treatment effect of laser depilation. A plurality of semiconductor laser beams are used as necessary to irradiate a wider area of skin surface at a time.

TECHNICAL FIELD

The present invention relates to a laser depilating method and a laserdepilating apparatus for depilating treatment with a laser beam from asemiconductor laser.

BACKGROUND ART

A conventional body hair depilating treatment (treatment for retardingor lowering the regrowth of hair) was performed by burning out hairroots by an electrical needle. This treating method must treat hair oneby one, taking a very long treating time and causing pain duringtreatment. Therefore, a laser depilating treatment is now being usedinstead of the depilating treatment using the electrical needle.

The laser depilating treatment is a treatment which retards the regrowth(growth) of hair by giving thermal or physical damage to a germinativecell and hair papilla of a hair bulb at the hair root and also to abulge and a sebaceous gland with a laser beam. For the conventionallaser depilating treatment, various types of laser irradiation devicessuch as a YAG laser (oscillation wavelength: approximately 1064 nm), aruby laser (oscillation wavelength: approximately 694 nm), analexandrite laser (oscillation wavelength: approximately 755 nm) and asemiconductor laser (oscillation wavelength: approximately 800 nm) asdescribed in, for example, Japanese National Stage Laid-Open PublicationNo. 2001-500529 (International Publication No. WO98/48716) are used.

Among them, a depilating treatment apparatus using the YAG laser or theruby laser is an apparatus which irradiates a skin surface with a highpower laser beam to directly destroy (e.g., thermolysis) a hair root, agerminative cell and the like. A laser beam of the YAG laser or the likehas a long wavelength and poor absorption efficiency by melanin in ahair root and germinative cell, and its power is high, so that itsirradiation time per irradiation is limited. Besides, the depilatingtreatment apparatus using the YAG laser utilizes a very expensivemedical laser irradiation device, and the depilating treatment must beperformed as medical treatment.

Meanwhile, a laser depilating apparatus using a small and inexpensivesemiconductor laser (laser diode) has a low power (e.g., approximately0.01 to 10 W) laser beam emitted from the semiconductor laser, so thatthe laser depilating treatment can be performed as cosmetic treatment.The semiconductor laser beam has a wavelength of, for example,approximately 780 to 810 nm. This laser beam having such a wavelength ishardly absorbed by water or blood but has very high absorptionefficiency by melanin in a hair root (hair shaft) and a germinativecell. Thus, the regrowth (growth) of hair can be retarded efficiently bythermal energy of the laser beam absorbed by the melanin.

As described above, the laser depilating apparatus using thesemiconductor laser has a feature that the semiconductor laser beam hasa wavelength suitable for the depilating treatment. However, theconventional laser depilating apparatus does not have an irradiationtime, irradiation energy and other various kinds of conditions forirradiation of the semiconductor laser beam examined adequately ordecided, so that an adequate depilating effect cannot be obtaineddepending on the situation or hair is reversely grown.

For example, Japanese Patent Unexamined Publication No. 2000-201726describes a laser depilating apparatus which is comprised of asemiconductor laser having light power of 5 to 1000 mW, light poweradjusting means for adjusting the light power of the laser beam emittedfrom the semiconductor laser, and irradiation time setting means forsetting an irradiation time of the laser beam. Here, the light power ofthe laser beam is adjusted by the on-time of the laser pulse, so thatthermal energy based on the irradiation of the laser beam might not beconducted effectively to the entire hair follicle tissue. Besides, thereis no suggestion about an energy density or the like of the laser beameffective for the depilating treatment.

Japanese Patent Unexamined Publication No. 2001-46141 describes a laserdepilating apparatus which is comprised of a laser diode for irradiatinga laser beam, a control section for controlling an irradiation time ofthe laser beam and an output control circuit for adjusting a voltage ora current applied to the laser diode. But, the above publication doesnot describe specific power of the laser beam (semiconductor laserbeam), an irradiation time or an energy density of the laser beameffective for depilating treatment.

Japanese Patent Unexamined Publication No. 2000-245525 describes lasertherapy equipment using an alexandrite laser (oscillation wavelength:approximately 755 nm) having a wavelength similar to that of thesemiconductor laser. Here, it is shown that the laser beam power isgenerally in a range of 10 to 40 J/cm² (0.1 to 0.4 J/mm²). However, thealexandrite laser has the same high power as the YAG laser does, so thatits laser irradiation time is limited to 10 to 40 msec. Besides, thehigh power alexandrite laser directly destroys (cauterizes) a hair rootand the like in the same way as the YAG laser to perform the depilatingtreatment, so that the depilating treatment cannot be performed byconducting the thermal energy of the laser beam to the entire hairfollicle tissue like the semiconductor laser.

In addition, the conventional laser depilating apparatus is difficult toincrease an irradiated area per treatment with the laser beam whilekeeping the energy density effective for depilating. Japanese PatentUnexamined Publication No. 2000-217938 describes a laser depilatingapparatus having a plurality of semiconductor lasers (laser diodes)which are circularly disposed. By using the plurality of semiconductorlasers, an irradiation area of the laser beam is increased. But, theplurality of semiconductor lasers circularly disposed are limited fromincreasing the irradiation area of the laser beam, and if theirradiation area is excessively increased, the laser beam might have anonuniform energy density.

Therefore, it is desired to increase an irradiation area of thesemiconductor laser beam so to improve the depilating effect of thesemiconductor laser beam. There is some consideration being made ondisposition of many laser diode elements in an array shape to use asemiconductor laser having high power equivalent to that of the YAGlaser. But, such a laser irradiation device has variations in powerdensity because the laser beams emitted from the individual diodeelements cause interference with each other. And, because thesemiconductor laser beam is designed to have high power, the feature ofthe semiconductor laser beam that the absorption efficiency by melaninis high cannot be utilized fully.

The present invention is to provide a laser depilating method and laserdepilating apparatus which can provide a laser depilating effect moresecurely and efficiently by utilizing the feature of the semiconductorlaser beam that the absorption efficiency by melanin in hair shafts andgerminative cells is high. Besides, it also provides a laser depilatingapparatus having a treatment region increased and a treatment speedimproved while keeping the depilating effect of the semiconductor laserbeam.

DISCLOSURE OF THE INVENTION

The laser depilating method of the present invention is a laserdepilating method for depilating treatment by irradiating a skin surfacewith a laser beam emitted from a semiconductor laser, comprisingirradiating a treatment region of the skin surface with the laser beamfor an irradiation time of 100 msec or more per irradiation whilecontrolling an energy density to a range of 0.01 to 1 J/mm² when theskin surface is irradiated with the laser beam; and performing thedepilating treatment by transmitting thermal energy based on theirradiation of the laser beam to the entire hair follicle tissue of thetreatment region. In the laser depilating method of the invention, thelaser beam (a semiconductor laser beam) emitted from the semiconductorlaser has a wavelength in a range of, for example, 750 to 900 nm.

The laser depilating apparatus of the invention is a laser depilatingapparatus, comprising a semiconductor laser for emitting a laser beamhaving a wavelength in a range of 750 to 900 nm; a radiating head havinga light path for guiding the laser beam and a laser irradiation surfaceso to irradiate a skin surface subject to depilating treatment with thelaser beam emitted from the semiconductor laser; an irradiationcondition control section for controlling an energy density to a rangeof 0.01 to 1 J/mm² when the skin surface is irradiated with the laserbeam while keeping the irradiation time of the laser beam at 100 msec ormore per irradiation.

According to the present invention, the irradiation time per irradiation(one time) of the semiconductor laser beam having the above-describedwavelength is controlled to 100 msec or more. Thus, it becomes possibleto effectively and efficiently use the thermal energy of thesemiconductor laser beam. In other words, when the irradiation time ofthe semiconductor laser beam is set to 100 msec or more, the thermalenergy of the semiconductor laser beam absorbed by melanin in the hairshafts and germinative cells can be conducted to the entire hairfollicle tissue (hair bulb, hair shaft, and connective tissue includingsheath, bulge, sebaceous gland and the like around the hair shaft). Thethermal damage is securely and efficiently applied to the entire hairfollicle tissue to exert an influence on the regrowth of hair, so thatthe regrowth of hair can be retarded without fail.

Even if the irradiation time per irradiation of the semiconductor laserbeam is simply extended, the thermal energy becomes insufficient and thethermal damage cannot be applied efficiently to the entire hair follicletissue if an energy density is insufficient when the semiconductor laserbeam is irradiated to a skin surface. Therefore, to obtain the hairregrowth retarding effect with reliability, the energy density of thesemiconductor laser beam is controlled to a range of 0.01 to 1 J/mm². Byusing the semiconductor laser beam having the above energy density, thethermal energy having a high depilating effect can be conveyed securelyand efficiently to the entire hair follicle tissue.

The laser depilating apparatus of the invention is further comprised ofthe semiconductor laser in plural numbers; and an optical system forgathering a plurality of laser beams emitted from the plurality ofsemiconductor lasers and forming so that the entire region of the laserirradiation surface of the radiation head is substantially irradiatedwith the laser beams. The radiating head has, for example, a rectangularlaser irradiation surface, and the plurality of semiconductor lasers aredisposed so that the plurality of laser beams irradiate substantiallydifferent regions in the rectangular laser irradiation surface.

By the laser depilating apparatus provided with the plurality ofsemiconductor lasers, the semiconductor laser beams having asubstantially constant power density can be collectively irradiated to awide rang of skin surface. The depilating treatment can be performed ona wide range by a single laser irradiation by increasing an irradiationrange (irradiation area) of the semiconductor laser beam. Therefore, atreating speed can be increased substantially without degrading thedepilating effect by the semiconductor laser beam.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a general structureof the laser depilating apparatus according to an embodiment of thepresent invention.

FIG. 2 is a front view showing a laser radiating probe of the laserdepilating apparatus of FIG. 1.

FIG. 3 is a vertical sectional view taken along line A—A of the laserradiating probe shown in FIG. 2.

FIG. 4 is a transverse sectional view taken along line B—B of the laserradiating probe shown in FIG. 2.

FIG. 5 is a view showing an irradiating state of a plurality ofsemiconductor laser beams in a laser irradiation surface of the laserradiating probe shown in FIG. 2.

FIG. 6 is a block view showing a structure of a drive control section ofa semiconductor laser of the laser depilating apparatus shown in FIG. 1.

FIG. 7 is a view illustrating an irradiation time of a semiconductorlaser beam according to one embodiment of the present invention.

FIG. 8 is a view illustrating a state of body hair which is a target oflaser depilating treatment.

FIG. 9 is a block diagram showing a structure of a drive control sectionof a semiconductor laser of the laser depilating apparatus according toanother embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Modes for practicing the present invention will be described.

FIG. 1 is a perspective view schematically showing a general structureof the laser depilating apparatus according to an embodiment of thepresent invention. In the drawing, 1 is a laser depilating apparatusbody having an operation panel 2, and the apparatus body 1 has therein amain power supply, a semiconductor laser power supply, a control circuitfor controlling the drive of a semiconductor laser, the operation of acompressor and the like, a circuit for a confirmation screen, and thelike.

A laser radiating probe 4 is connected to the laser depilating apparatusbody 1 through a cable 3. The laser radiating probe 4 is configured tobe freely movable by an angle adjusting arm 5. The cable 3 containstherein lead wires for connecting the semiconductor laser power supplyof the apparatus body 1 and between the control circuit and the laserradiating probe 4, an air tube for supplying air from the compressor tothe laser radiating probe 4, and the like.

The laser depilating apparatus body 1 has a CCD camera-mountedconfirmation probe which is not shown. Laser depilating treatment can beperformed while checking a skin surface with an image taken by the CCDcamera of the confirmation probe. The image taken by the CCD camera isshown on a color liquid crystal screen 6 of the operation panel 2. Onthe operation panel 2, a touch-sensitive operation screen 7, a mainpower switch (not shown) and the like are disposed.

FIG. 2, FIG. 3 and FIG. 4 are views showing a structure of the laserradiating probe 4. FIG. 2 is a front view of the laser radiating probe4, FIG. 3 is a vertical sectional view taken along line A—A of FIG. 2,and FIG. 4 is a transverse sectional view taken along line B—B of FIG.2. As shown in these drawings, a plurality of semiconductor lasers 8, 8. . . are disposed as a laser source within the laser radiating probe 4.The number of semiconductor lasers 8 is not limited to be multiple, buta single semiconductor laser can be used to configure the laserdepilating apparatus. When the plurality of semiconductor lasers 8 areused, the semiconductor lasers 8 are used in the number of, for example,2 to 50. The laser depilating apparatus of this embodiment has 20semiconductor lasers 8 as described later.

For the semiconductor lasers 8, laser diodes which emit laser beamshaving a wavelength in a range of, for example, 750 to 900 nm are used.The laser beams having a wavelength in a range of 750 to 900 nm providefavorable depilating effects because, for example, they relativelydeeply penetrate the skin of a human body and are absorbed by melanin ina hair shaft and germinative cell with priority as compared with wateror blood (hemoglobin). In other words, a laser beam having a wavelengthof less than 750 nm is absorbed at a high rate by melanin but alsoabsorbed substantially by blood or the like, possibly loweringutilization efficiency of a laser beam for depilating treatment anddamaging the skin and the like. Meanwhile, when a laser beam has awavelength of exceeding 900 nm, the absorption factor by melanin lowers,and a favorable depilating effect cannot be obtained. It is particularlydesirable that the semiconductor laser beam has a wavelength in a rangeof 780 to 810 nm (800 nm as median).

The semiconductor laser 8 preferably has a power of 0.1 W or more. Asemiconductor laser having a power of less than 0.1 W can be used, butthe laser beam might not penetrate the skin sufficiently, thoughvariable depending on the wavelength of such a low power semiconductorlaser. Such a laser beam does not adequately reach the hair bulb and thelike, so that a favorable depilating effect cannot be obtained, and hairmight be restored depending on circumstances. The semiconductor laser 8preferably has a power of 0.5 W or more, and more preferably 1 W ormore, in order to penetrate the laser beam effectively into the skin.

But, if the semiconductor laser has an excessively high power, it isnecessary to reduce an irradiation time of the laser beam, thoughvariable depending on a spot size. Therefore, the thermal energy by thesemiconductor laser beam might not be distributed over the entire hairfollicle tissue. Therefore, the semiconductor laser 8 preferably has apower of 50 W or less. Thus, the present invention desirably uses thesemiconductor laser 8 having a power in a range of 0.1 to 50 W. Thesemiconductor laser 8 has more preferably a power in a range of 0.5 to10 W, and still more preferably in a range of 1 to 10 W.

The spot size (laser radiation area of one semiconductor laser 8) ofeach semiconductor laser 8 is ideally about 2 to 4 times of apenetration depth of the laser beam. It is necessary to consider thepower of the semiconductor laser 8, but it is desirable in practice thatan irradiation area of a laser beam by the semiconductor laser 8 is setto a range of 0.5 to 20 mm². The spot size (laser radiation area) ofeach semiconductor laser 8 is desirably set to a range of 0.5 to 10 mm²,and more desirably in a range of 0.7 to 8 mm².

The plurality of semiconductor lasers 8, 8 . . . are held by a holdingmember 9 having a substantially spherical laser holding surface. Lenses(e.g., spherical lenses) 10, 10 . . . are respectively disposed in frontof radiation by the plurality of semiconductor lasers 8, 8 . . . . Thelaser beams emitted by the individual semiconductor lasers 8 are focusedon a radiating head 11 through the individual lenses 10. The radiatinghead 11 is made of, for example, quartz glass and makes a substantialcontact with a skin surface which is subject to the laser depilatingtreatment.

The radiating head 11 has a light path therein to guide the individualsemiconductor laser beams to a prescribed treatment region of a skinsurface. The front face of the radiating head 11 is a laser irradiationsurface 12. The individual laser beams emitted from the plurality ofsemiconductor lasers 8, 8 . . . are focused into the radiating head 11by the lenses 10, 10 . . . . The individual semiconductor laser beamsare determined to have light paths so to pass through prescribedportions in the radiating head 11 and shaped to have a spot sizesuitable for the laser depilation within the radiating head 11. Theindividual light paths in the radiating head 11 are set to radiate asubstantially entire region of the laser irradiation surface 12 with thesemiconductor laser beams. Therefore, the plurality of semiconductorlaser beams are radiated to a skin surface corresponding to the area ofthe laser irradiation surface 12.

A relationship between the state of holding the plurality ofsemiconductor lasers 8, 8 . . . and the irradiation region of theplurality of semiconductor laser beams will be described in furtherdetail. The laser depilating apparatus of this embodiment has, forexample, 20 semiconductor lasers 8, 8 . . . . These 20 semiconductorlasers 8, 8 . . . are basically disposed in the shape of a matrix with 5rows and 4 columns.

The holding member 9 for holding these 20 semiconductor lasers 8, 8 . .. has a laser holding surface which is spherical in the verticalsectional direction in FIG. 3 and circumflex in the transverse sectionaldirection in FIG. 4. The 20 semiconductor lasers 8, 8 . . . are set bythe holding member 9 to have optical axes so that rays of light aregathered into the radiating head 11. The 20 semiconductor lasers 8, 8 .. . are held by the holding member 9 having the above-described laserholding surface in such a way that a distance from the each lightemitting point to the light-gathering point in the radiating head 11becomes substantially constant.

Meanwhile, the radiating head 11 has a rectangular laser irradiationsurface 12. The laser irradiation surface 12 has a shape of, forexample, 15×12 mm. In other words, the radiating head 11 has a laserradiation area of 15×12 mm (area=180 mm²). The area of the laserirradiation surface 12 can be set appropriately according to thedisposed number of semiconductor lasers 8, the contents of treatment andthe like. When one semiconductor laser is used, its spot size becomes alaser radiation area. When a plurality of semiconductor lasers are used,the laser irradiation surface 12 preferably has an area of 15 mm² ormore, and more preferably 50 mm² or more.

The semiconductor laser beams emitted from the individual semiconductorlasers 8 are formed to have prescribed spot sizes according to gatheringof light according to the individual lenses 10, refraction at the timeof incidence to the radiating head 11 and a length of light path by theradiating head 11. Besides, the individual semiconductor laser beams areset to have light paths so to pass through prescribed portions in theradiating head 11 depending on the shape of the holding member 9, thestate of holding the semiconductor lasers 8 by the holding member 9, apositional relationship between the semiconductor lasers 8 and theradiating head 11, and the like. The individual light paths aredetermined in such a way that the semiconductor laser beams respectivelyirradiate substantially different regions in the laser irradiationsurface 12, and the entire region of the laser irradiation surface 12 issubstantially irradiated with the semiconductor laser beams.

As shown in FIG. 5, a plurality of semiconductor laser beams X, X . . .are configured to have light paths so to irradiate substantiallydifferent regions in the laser irradiation surface 12. The irradiationpositions in the laser irradiation surface 12 by the plurality ofsemiconductor laser beams X, X . . . are in a matrix with 5 rows and 4columns according to the number of semiconductor lasers 8 so to cover asubstantially entire region of the laser irradiation surface 12. And,the rectangular laser irradiation surface 12 is substantially irradiatedits entire region with the plurality of semiconductor laser beams X, X .. . .

The state of irradiation of the substantially different regions in thelaser irradiation surface 12 with the plurality of semiconductor laserbeams X, X . . . is adequate when the individual semiconductor laserbeams X have at least different irradiation centers, and the neighboringsemiconductor laser beams X may have somewhat overlapped irradiationranges. The state that the entire region of the laser irradiationsurface 12 is substantially irradiated with the plurality ofsemiconductor laser beams X, X . . . may be a state that it provides adepilating effect on the entire skin surface equivalent to the area ofthe laser irradiation surface 12 with the semiconductor laser beams X.There may be a small gap formed between the irradiation ranges of theneighboring semiconductor laser beams X, and even in such a case, thedepilating effect can be provided by irradiation heat of thesemiconductor laser beams X.

The plurality of semiconductor laser beams X, X . . . each have asubstantially constant power density. Therefore, the laser beams havinga substantially constant power density are collectively irradiated tothe laser irradiation surface 12 of the radiating head 11. A skinsurface is irradiated with the semiconductor laser beams X depending onthe area of the rectangular laser irradiation surface 12, so that thelaser beams having a substantially constant power density arecollectively irradiated into the treatment region of the skin surface.The laser irradiation surface 12 (irradiation area: 180 mm²) of thelaser depilating apparatus of this embodiment has a shape of, forexample, 15×12 mm. Therefore, a skin surface having substantially thesame area can be irradiated with the semiconductor laser beams Xcollectively. By the laser depilating apparatus of this embodiment, itis possible to expand the region of depilating treatment per laserirradiation according to the irradiation state with the plurality ofsemiconductor laser beams X, X . . . .

A plurality of cooling air nozzles 13 are formed around the radiatinghead 11 of the laser radiating probe 4. Cooling air is supplied before,simultaneously with or after irradiation with the semiconductor laserbeams. The temperature of the skin also rises slightly when the skinsurface is irradiated with the semiconductor laser beams, but damage tothe skin can be retarded more securely by blowing cooling air to theskin surface when irradiated with the semiconductor laser beams. Coolinggel or the like may also be used when irradiated with the semiconductorlaser beams.

In the laser depilating apparatus of the above embodiment, a skinsurface is irradiated with the semiconductor laser beams for anirradiation time of 100 msec or more per one time of irradiation whilecontrolling an energy density to a range of 0.01 to 1 J/mm² when theskin surface of a human body subject to the depilating treatment isirradiated. When the skin surface is irradiated with the semiconductorlaser beams, an energy density E is controlled by at least one of anirradiation time T and a power density L of the semiconductor laserbeams. The above irradiation conditions of the semiconductor laser beamssatisfy a relationship of an energy density E [J/mm²]=power density L[W/mm²]×irradiation time T [sec]. Therefore, the energy density iscontrolled to a desired range by adjusting the irradiation time T and/orthe power density L of the semiconductor laser beams.

In practice, the power density L of the laser beams by the semiconductorlasers 8 is preferably determined to fall in a range of 0.01 to 5 W/mm²depending on the irradiation time T. If the power density L of thesemiconductor laser beams in the irradiation region is less than 0.01W/mm², an adequate depilating effect might not be obtained even if theirradiation time per irradiation of the semiconductor lasers 8 isextended. Meanwhile, when the semiconductor laser beams have a powerdensity L of exceeding 5 W/mm², the irradiation time per one time cannotbe determined to be long enough, and the thermal energy might not bedistributed to cover the entire hair follicle tissue. It is desirablethat the power density L of the semiconductor laser beams is set to arange of 0.05 to 2 W/mm².

The power density L of the semiconductor laser beams is determinedaccording to power C of the semiconductor lasers 8 and spot size S ofthe semiconductor laser beams. In other words, it meets the relationshipof power density L [W/mm²]=power C [W]/spot size S [mm²]. The spot sizeS is basically determined to be constant, so that the power density L ofthe semiconductor laser beams is controlled according to the power C ofthe semiconductor lasers 8. The output (light output) C of thesemiconductor lasers 8 is controlled by a voltage value or current valueinput to the semiconductor laser (laser diode) 8.

The light output of the semiconductor laser beams can also be controlledby, for example, varying the on-time of the laser pulse with thesemiconductor lasers 8 as pulse oscillation. But, the pulsedsemiconductor laser beam cannot convey the thermal energy to the entirehair follicle tissue efficiently. The semiconductor lasers 8 are desiredto be continuously oscillated in order to enhance the transmissionefficiency of the thermal energy. Therefore, the light output of thesemiconductor lasers 8 is controlled by the voltage value or currentvalue input to the semiconductor lasers 8.

FIG. 6 is a block view showing a structure of the drive control sectionof the semiconductor lasers 8. A control section 101 reads controlsignals for the drive conditions (voltage or current value) and drivetime (laser beam irradiation time) of the semiconductor lasers 8 from astorage section 103 according to a treatment mode or the like input froman operation section 102. Among the control signals read from thestorage section 103, the drive condition signal for the semiconductorlasers 8 is sent from the control section 101 to a laser drive circuit105 via a D/A conversion circuit 104. The drive time signal for thesemiconductor lasers 8 is sent from the control section 101 to the laserdrive circuit 105.

According to the control signal, the laser drive circuit 105 inputs aprescribed voltage value or current value from an unshown laser drivepower supply to the semiconductor lasers 8. Time of applying an inputcurrent is controlled by the laser drive circuit 105 according to thecontrol signal. Thus, the power C and drive time (a laser beamirradiation time T) of the semiconductor lasers 8 are controlled. Thespot size S of the semiconductor laser beams is basically determined tobe constant, so that the power density L of the semiconductor laserbeams is controlled by the power C of the semiconductor lasers 8.

The drive time (laser beam irradiation time T) of the semiconductorlasers 8 is set to 100 msec or more. After meeting the above condition,energy density E at the irradiation of a skin surface with thesemiconductor laser beams is controlled according to the power density Land the irradiation time T of the semiconductor laser beams. Theirradiation energy density E of the semiconductor laser beams isspecifically controlled to a range of 0.01 to 1 J/mm². And, a skinsurface is irradiated with the semiconductor laser beams having theabove irradiation time T and irradiation energy density E to perform thedepilating treatment by conveying the thermal energy based on theirradiation of the semiconductor laser beams to the entire hair follicletissue.

It is important that a treatment region of the skin surface isirradiated with the semiconductor laser beams for an irradiation time of100 msec or more per irradiation. Here, the irradiation time perirradiation of the semiconductor laser beam is a lighting time (ON-time)T per treatment by the semiconductor laser 8 as shown in FIG. 7. Thesemiconductor lasers 8 are basically driven by continuously oscillating,so that the irradiation time per irradiation of the semiconductor laserbeam corresponds to the irradiation time per treatment.

As described above, the thermal energy of the laser beams absorbed bymelanin in the hair shaft and germinative cell can be conducted to theentire hair follicle tissue by irradiating a skin surface with thesemiconductor laser beams determined to have the irradiation time T of100 msec or more per irradiation. Specifically, when a skin surface 21is irradiated with the semiconductor laser beams X with the irradiationtime T set to 100 msec or more per irradiation as shown in FIG. 8, thesemiconductor laser beams X penetrate the skin and are selectivelyabsorbed by melanin contained in a hair shaft 22 and a germinative cell24 of a hair bulb 23. The hair shaft 22 and the germinative cell 24having selectively absorbed the semiconductor laser beams X are heatedto a prescribed temperature of, for example, about 60 to 100° C. by thethermal energy of the semiconductor laser beams X.

At this time, the irradiation time T of the semiconductor laser beams Xper irradiation is set long to be 100 msec or more. Therefore, thethermal energy absorbed by the melanin in the hair shaft 22 and thegerminative cell 24 is sufficiently propagated to their peripheries.Accordingly, the hair shaft 22, the germinative cell 24 and a hairpapilla 25, and the entire hair follicle tissue including a sheath 26 asconnective tissue around them, a stem tissue 27, a sebaceous gland 28and a bulge 29 can be heated securely and efficiently to a temperatureeffective for depilating. A region having a temperature of approximately60 to 100° C. which is considered to be effective for depilating isapproximately equal to or larger than a diameter of the hair follicle,and thermal damage is applied to a region having such a temperature.

As described above, when the semiconductor laser beam X is determined tohave the irradiation time T of 100 msec or more per irradiation, thethermal damage can be given effectively and securely to the entire hairfollicle tissue. And, the regrowth of hair can be retarded surely byapplying thermal damage to the entire hair follicle tissue, namely notonly the hair shaft 22 and the germinative cell 24 but also the sheath26 as the connective tissue and the stem tissue 27, the sebaceous gland28 and the bulge 29 with the semiconductor laser beams X. In otherwords, the depilating effects based on the hair growth retarding effectand the reducing effect can be obtained securely and efficiently. Inaddition, the depilating treatment can be performed safely because theskin can be prevented from having a high temperature.

Meanwhile, when the semiconductor laser beam has an irradiation time Tof less than 100 msec per irradiation, the thermal energy is notconducted sufficiently by the semiconductor laser beams having the samepower density as above, and thermal damage cannot be given adequately tothe entire hair follicle tissue. When the power density of thesemiconductor laser beams is increased to a level capable of attainingthe depilating effects, the hair shaft 22 and the germinative cell 24are excessively heated to cause a thermally insulated state and sufferfrom decomposition and vaporization. It means that the absorber for thesemiconductor laser beams is lost, and a temperature is caused to dropby the heat of vaporization. Thus, the thermal damage cannot be giveneffectively to the entire hair follicle tissue. Besides, the skintemperature might become high, and a side effect might be caused as aresult.

The irradiation time T per irradiation of the semiconductor laser beamscan be set appropriately to a range of retarding the skin from having ahigh temperature or damage resulting from it but preferably set to 10sec or less in view of practical use. The irradiation time T perirradiation of the semiconductor laser beams is preferably set to 100msec or more and 10 sec or less. Besides, the irradiation time T perirradiation of the semiconductor laser beams X is particularly desiredto be in a range of 1 to 5 sec considering the laser depilating effectand safety.

Not only the irradiation time T per irradiation of the semiconductorlaser beam but also the energy density E of the semiconductor laser beamare pertinent to the laser depilating effect. Specifically, even if theirradiation time T per irradiation of the semiconductor laser beam isset to be long, the thermal damage cannot be given efficiently to theentire hair follicle tissue when the energy density E of thesemiconductor laser beam is excessively low. Therefore, the energydensity E of the semiconductor laser beam is controlled to a range of0.01 to 1 J/mm² while keeping the irradiation time T per irradiation ofthe semiconductor laser beam to 100 msec or more.

As described above, the energy density E and the irradiation time Tsatisfy the relationship of the energy density E [J/mm²]=power density L[W/mm²]×irradiation time T [sec]. Therefore, the energy density E of thesemiconductor laser beams is controlled to a range of 0.01 to 1 J/mm² byadjusting the irradiation time T and the power density L of thesemiconductor laser beams while the irradiation time T per irradiationof the semiconductor laser beam is kept to 100 msec or more. When thesemiconductor laser beams having the energy density E are used, it ispossible to conduct the thermal energy having a high depilating effectto the entire hair follicle tissue securely and efficiently.

When the energy density E of the semiconductor laser beams is less than0.01 J/mm², the thermal damage cannot be given to the entire hairfollicle tissue. Meanwhile, when the energy density E exceeds 1 J/mm²,the hair shafts and germinative cells might be decomposed, the skinmight have a high temperature, and a side effect might be caused as aresult. The energy density E of the semiconductor laser beam isespecially desired to be controlled to a range of 0.1 to 0.4 J/mm². Thisirradiation energy density E can give thermal damage to the hairfollicle tissue more effectively.

As described above, the thermal damage can be caused effectively andsecurely to the entire hair follicle tissue with the semiconductor laserbeam which is set to have the irradiation time T of 100 msec or more perirradiation and the irradiation energy density E controlled to a rangeof 0.01 to 1 J/mm². Thus, an effect of retarding the growth of hair andan effect of lowering it can be obtained securely and efficiently.Specifically, it becomes possible to obtain the laser depilating effectssecurely and efficiently by making use of a feature of the semiconductorlaser beam that the absorption efficiency by melanin in hair shafts andgerminative cells is high. In addition, the depilating treatment can beperformed safely because the skin temperature does not become high.

Besides, the laser depilating apparatus of this embodiment emits thelaser beams having a substantially constant power density from the laserirradiation surface 12 of the radiating head 11 by gathering theplurality of laser beams emitted from the plurality of semiconductorlasers 8, 8 . . . and forming. An irradiation range (irradiation area)of the semiconductor laser beams having the substantially constant powerdensity is substantially expanded, so that the depilating treatment canbe performed on a large region by a single laser irradiation. Therefore,it is possible to enhance a depilating treatment speed extensivelywithout lowering the depilating effects by the semiconductor laserbeams.

Especially, the laser depilating apparatus of this embodiment has theplurality of semiconductor lasers 8, 8 . . . disposed in a matrix with mrows and n columns and irradiates the rectangular laser irradiationsurface 12 with the plurality of semiconductor laser beams correspondingto the disposed state. The entire region of the rectangular laserirradiation surface 12 is irradiated with the semiconductor laser beamshaving the substantially constant power density collectively, so that aregion which can be treated by a single laser irradiation can beenlarged substantially as compared with an existing laser depilatingapparatus having a plurality of semiconductor lasers disposed in acircular form. Besides, the depilating effect in the enlarged laserirradiation region can be enhanced more uniformly.

Specific laser depilating treatment is performed by first shaving hairon a skin surface and applying cooling gel or the like to the treatmentregion. In the laser depilating treatment process, the treatment time isset to, for example, 5 to 60 minutes, and the semiconductor laser beamsare repeatedly irradiated and suspended within the treatment time. Thesemiconductor laser beams are irradiated while gradually moving theirpositions on the skin surface. The irradiation time of the semiconductorlaser beams is determined as a lighting time per irradiation asdescribed above. While the irradiation of the semiconductor laser beamsis being suspended, cooling air is blown from the air nozzles 13 to theskin surface to retard the temperature increase of the skin. Thus, thedepilating treatment is performed.

The laser depilating apparatus of this embodiment was used to actuallyperform the laser depilating treatment to find that a favorabledepilating effect could be obtained by irradiating the lasers under theabove-described conditions. Specifically, the laser depilating treatmentwas performed by irradiating a leg of a subject with the semiconductorlaser beams (800 nm as median) with the irradiation time T set to 3 secper irradiation while controlling the semiconductor laser beams to havean energy density in a range of 0.1 to 0.4 J/mm² at the time of theirradiation. The laser depilating treatment was performed for eightweeks. The laser treatment was performed two times a week for the firstfour weeks and one time a week for the next four weeks. It was confirmedas a result that plural subjects had favorable depilating effects(reduction in number of hair, reduction in hair shaft diameter (thinhair), decrease of pigment in hair, etc.).

Meanwhile, as a comparative example of the present invention, theirradiation time T of the semiconductor laser beams was lowered to 40msec per irradiation with the same power of the semiconductor lasers toperform the same treatment for eight weeks as the above-describedembodiment to find that favorable depilating effects could not beobtained. Besides, when the irradiation time T of the semiconductorlaser beams was set to 40 msec per irradiation and the irradiationenergy density was controlled to a range of 0.1 to 0.4 J/mm², thefavorable depilating effects could not be obtained either.

As described above, it is possible to obtain the laser depilatingeffects more securely and efficiently by utilizing the features of thesemiconductor laser beams that the absorption efficiency by melanin inhair shafts and germinative cells is high by the laser depilatingapparatus and the laser depilating treatment using it of thisembodiment. In the above-described embodiment, the use of the pluralityof semiconductor lasers was described, but the invention is not limitedto it and can also be applied to a laser depilating apparatus using asingle semiconductor laser.

In addition, all the plurality of semiconductor lasers 8, 8 . . . arenot required to come on during the treatment, and only desiredsemiconductor lasers may be lit depending on a treatment area, a shapeof treatment region and the like. FIG. 9 is a block view showing astructure of the laser drive control section according to anotherembodiment of the invention. The laser depilating apparatus of thisembodiment sends a drive time signal for the semiconductor laser 8 fromthe control section 101 to the laser drive circuit 105 via a switchcircuit 106. A control signal is sent from the control section 101 tothe switch circuit 106 to turn on the switch of the semiconductor lasersso to light among the plurality of semiconductor lasers 8, 8 . . . .

Thus, the laser beams can be emitted from only desired semiconductorlasers among the plurality of semiconductor lasers 8, 8 . . . .Selection of desired semiconductor lasers enables to change a laserdepilating treatment area. This configuration is effective in changing atreatment area or a treatment portion by a single laser radiating probe4.

INDUSTRIAL APPLICABILITY

According to the laser depilating method and laser depilating apparatusof the present invention, it becomes possible to obtain the depilatingeffects more securely and efficiently by utilizing the feature of thesemiconductor laser beams that an absorption efficiency by melanin inhair shafts and germinative cells is high. Such a laser depilatingmethod and laser depilating apparatus are effectively used for variouskinds of depilating treatments. Besides, a treatment region can beincreased by using a plurality of semiconductor lasers, and it becomespossible to enhance a depilating treatment speed.

1. A laser depilating apparatus, for retarding a regrowth of haircomprising: a semiconductor laser for emitting a laser beam having awavelength in a range of 750 to 900 nm and a power density in a range of0.01 to 5 W/mm²; a radiating head having a light path for guiding thelaser beam and a laser irradiation surface so as to irradiate a skinsurface subject to depilating treatment with the laser beam emitted fromthe semiconductor laser; and an irradiation condition control sectionfor controlling an irradiation time of the laser beam to 100 msec ormore per irradiation and an energy density to a range of 0.01 to 1J/mm², and configured such that an entire hair follicle tissue of theskin surface is heated to a temperature greater than 60° C. and lessthan 100° C. so that the regrowth of hair can be retarded throughthermal damage to the entire hair follicle tissue when the skin surfaceis irradiated with the laser beam.
 2. The laser depilating apparatusaccording to claim 1, wherein the irradiation condition control sectioncontrols at least one selected from the irradiation time and the powerdensity of the laser beam to make the laser beam having the energydensity in the range of 0.01 to 1 J/mm².
 3. The laser depilatingapparatus according to claim 2, wherein the irradiation conditioncontrol section controls the irradiation time of the laser beam to therange of 100 msec or more and 10 sec or less per irradiation.
 4. Thelaser depilating apparatus according to claim 1, wherein the laser beamhas the wavelength in the range of 780 to 810 nm.
 5. The laserdepilating apparatus according to claim 1, wherein the semiconductorlaser is one of a plurality of semiconductor lasers, the laserdepilating device further comprising: an optical system for gatheringand forming a plurality of laser beams emitted from the plurality ofsemiconductor lasers so as to have the entire region of the laserirradiation surface of the radiating head substantially irradiated withthe laser beams.
 6. The laser depilating apparatus according to claim 5,wherein the radiating head has the laser irradiation surface in arectangular shape, and the plurality of semiconductor lasers aredisposed to respectively irradiate substantially different regions inthe rectangular laser irradiation surface with the plurality of laserbeams.
 7. The laser depilating apparatus according to claim 6, whereinthe plurality of semiconductor lasers are supported by a member having aspherical holding surface so as to have substantially constant distancesfrom individual light emitting points to a light-gathering point in theradiating head.
 8. The laser depilating apparatus according to claim 5,further comprising: a laser switching section for emitting the laserbeam from any semiconductor laser among the plurality of semiconductorlasers.
 9. The laser depilating apparatus according to claim 1, whereinthe irradiation condition control section controls the irradiation timeof the laser beam to 1 sec or more.
 10. The laser depilating apparatusaccording to claim 1, wherein the hair follicle tissue includes a hairshaft, a germinative cell, a sheath as connective tissue, a stem tissue,a sebaceous gland and a bulge.
 11. The laser depilating apparatusaccording to claim 10, wherein the laser beam with the irradiation timeof 100 msec or more per irradiation is absorbed by the hair shaft andthe germinative cell, and the thermal energy of the laser beam absorbedby the hair shaft and the germinative cell is propagated to the hairfollicle tissue so that the thermal damage is applied to the entire hairfollicle tissue.
 12. The laser depilating apparatus according to claim1, wherein the irradiation time of the laser beam corresponds to theirradiation time per treatment for depilating.